A cheap dust filter would be a box fan and a furnace filter--both new. Even if it won't work, you have an air circulator. For heavy duty filtration, you need a good air filter--HEPA, if possible. Be ready to pay through the schnozz for the filters--there are no washable HEPA or even near HEPA that ...

Hi, This isn't really cpap-specific but more about allergies, so sorry if it's off topic. I just figured you guys might know a lot about humidifiers and the like. I have a question about running a humidifier without water just as an air filter. I get allergies really bad in the spring, which is just...